Vocal correlates of sender-identity and arousal in the isolation calls of domestic kitten (Felis silvestris catus)

We recorded calls of 18 kittens in an experimentally-induced separation paradigm, where kittens were spatially separated from their mother and siblings. In the Low arousal condition, infants were just separated without any manipulation. In the High arousal condition infants were handled by the experimenter. Multi-parametric sound analyses revealed that kitten isolation calls are individually distinct and differ between the Low and High arousal conditions. Our results suggested that source- and filter-related parameters are important for encoding sender-identity, whereas time-, source- and tonality-related parameters are important for encoding arousal.Comparable findings in other mammalian lineages provide evidence for commonalities in non-verbal cues encoding sender-identity and arousal across mammals comparable to paralinguistic cues in humans. This favours the establishment of general concepts for voice recognition and emotions in humans and animals.Human speech and non-linguistic vocalisations convey paralinguistic cues encoding the physical characteristics of a speaker, termed here indexical cues (e.g., sex, age, body size, sender-identity), and the emotional state of a sender, termed here prosodic cues (e.g., emotional valence, arousal) (e.g., [1-3]). Whereas linguistic aspects of human speech are unique to humans, non-verbal cues comparable to paralinguistic cues were also found in the vocalisations of animals of at least 11 mammalian orders (for indexical cues e.g., humans: [3,4], non-human primates: [5,6], Scandentia: [7]; Artiodactyla: [8,9]; Perissodactyla: [10,11]; Carnivora: [12,13]; Cetaceae: [14]; Chiroptera: [15,16]; Rodentia: [17,18]; Proboscidae: [19,20]; Sirenia: [21]; Hyracoidea: [22]; for prosodic cues see review [23-25]). This suggests a pre-human origin of paralinguistic cues due to homologies in the central nervous system and the mammalian vocal production system.In mammals vocal production is based on a highly evolutionarily conserved system.